Along with the high integration of semiconductor devices, the miniaturization of their components has also advanced. For a dynamic random access memory (DRAM), a high-capacity capacitor of very small area is required. Ferroelectric thin films with extremely large relative permittivity have attracted consideration for making such capacitors. As a well-known example, the work of P. J. Bhattacharya et al. is mentioned in Japan J. Appl. Phys., Vol. 32 (1993), pp. 4103-4106.
Bhattacharya et al. understood that when a (Ba, Sr)TiO.sub.3 (hereafter "BST") film was formed on a Pt substrate, the crystals of the film grew in a columnar shape, enabling a high relative permittivity of 300 to be achieved. However, when capacitors were made using this thin film, there were many with a large leakage current and short-circuits in the initial stage, so it was difficult to use them for ultra large scale integration (ULSI) such as DRAM. As a result of reviewing such problems in detail, it became understood that the process for forming an upper electrode was related. When capacitors are formed using these thin films, metallic materials such as Pt are often deposited on the film as an upper electrode by sputtering, electron-beam vapor deposition, etc.
When the upper electrode was formed by these methods, a leakage current was generated through the dielectric film, and it was difficult to use dielectric as a capacitor for DRAM. Accordingly, one object of the invention is to provide a method for making a ferroelectric thin film capacitor in which leakage current is kept small even if the upper electrode is deposited on the ferroelectric dielectric film by sputtering or electron-beam vapor deposition.